Excitation-dependent energy transfer and color tunability in Dy3+/Eu3+ co-doped multi-component borophosphate glasses

Using the melt-quench technique, potassium zinc borophosphate (KZnBP) glasses incorporated with Dy3+, Eu3+, and Dy3+/Eu3+ ions individually and combinedly were prepared, and their photoluminescence (PL)-related features were investigated. The KZnBP glass containing an optimized content of Dy3+ (0.5 mol%) is co-doped with Eu3+ in various contents, and the energy transfer (ET) process between them was studied at lambda(exci) = 349, 364, 387 (Dy3+), and 394 nm (Eu3+). The Dy3+/Eu3+ co-doped system, when excited with Dy3+ excitations has resulted in a significant decrease in the intensity of Dy3+ peaks observed at 480 nm (F-4(9/2)-> H-6(15/2), blue) and 574 nm (F-4(9/2)-> H-6(13/2), yellow), with simultaneous enhancement of the intensity of Eu3+ peaks at 591 nm (D-5(0)-> F-7(1), orange) and 617 nm (D-5(0)-> F-7(2), red). This trend is due to the efficient energy transfer from Dy3+ to Eu3+, indicating that Eu3+ ions were sensitized by Dy3+ ions. Dexter's theory and the Inokuti-Hirayama (I-H) model revealed that the dipole-dipole interaction is accountable for the energy transfer from Dy3+ to Eu3+ through energy-transfer channels [F-4(9/2)(Dy3+)+F-7(1,2)(Eu3+)-> H-6(15/2)(Dy3+)+D-5(2)(Eu3+)] and [F-4(9/2)(Dy3+)+F-7(0)(Eu3+)-> H-6(13/2)(Dy3+)+D-5(0)(Eu3+)]. The color coordinates of the Dy3+/Eu3+ co-doped glasses under various excitations fall within the white light emission spectrum, indicating their potential application in warm white LEDs.